[unity] Fixed null reference exception upon import when default shader is used but preferences has default shader set to a non-existing/null shader path.

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Utility/AssetUtility.cs

@@ -575,22 +575,23 @@ namespace Spine.Unity.Editor {
 					pageName = "Material";
 
 				string materialPath = assetPath + "/" + primaryName + "_" + pageName + ".mat";
-				Material mat = (Material)AssetDatabase.LoadAssetAtPath(materialPath, typeof(Material));
+				Material material = (Material)AssetDatabase.LoadAssetAtPath(materialPath, typeof(Material));
 
-				if (mat == null) {
-					mat = new Material(Shader.Find(SpineEditorUtilities.Preferences.defaultShader));
-					ApplyPMAOrStraightAlphaSettings(mat, SpineEditorUtilities.Preferences.textureSettingsReference);
-					AssetDatabase.CreateAsset(mat, materialPath);
+				if (material == null) {
+					Shader defaultShader = Shader.Find(SpineEditorUtilities.Preferences.DefaultShader);
+					material = defaultShader != null ? new Material(defaultShader) : null;
+					ApplyPMAOrStraightAlphaSettings(material, SpineEditorUtilities.Preferences.textureSettingsReference);
+					AssetDatabase.CreateAsset(material, materialPath);
 				} else {
-					vestigialMaterials.Remove(mat);
+					vestigialMaterials.Remove(material);
 				}
 
 				if (texture != null)
-					mat.mainTexture = texture;
+					material.mainTexture = texture;
 
-				EditorUtility.SetDirty(mat);
+				EditorUtility.SetDirty(material);
 				// note: don't call AssetDatabase.SaveAssets() since this would trigger OnPostprocessAllAssets() every time unnecessarily.
-				populatingMaterials.Add(mat); //atlasAsset.materials[i] = mat;
+				populatingMaterials.Add(material); //atlasAsset.materials[i] = mat;
 			}
 
 			atlasAsset.materials = populatingMaterials.ToArray();

spine-unity/Assets/Spine/Editor/spine-unity/Editor/Windows/SpinePreferences.cs

@@ -66,6 +66,10 @@ namespace Spine.Unity.Editor {
 
 		internal const string DEFAULT_DEFAULT_SHADER = "Spine/Skeleton";
 		public string defaultShader = DEFAULT_DEFAULT_SHADER;
+		public string DefaultShader {
+			get { return !string.IsNullOrEmpty(defaultShader) ? defaultShader : DEFAULT_DEFAULT_SHADER; }
+			set { defaultShader = value; }
+		}
 
 		internal const float DEFAULT_DEFAULT_ZSPACING = 0f;
 		public float defaultZSpacing = DEFAULT_DEFAULT_ZSPACING;